1. Field Of The Invention
The invention relates generally to apparatus and methods for controlling engine operation, and more particularly to apparatus and methods for determining the position of a sensor used for controlling engine operation.
2. Description Of The Related Art
It is generally known to provide engine control systems including one or more sensors for detecting a condition of engine operation and for generating a corresponding control signal used by the control system. An example of such a control system is a throttle control system for an internal combustion engine. Such a system typically includes a throttle lever, a throttle on the engine, and a linkage operably connecting the throttle lever to the throttle. The system may also typically include a throttle position sensor for generating a throttle position control signal used by an electronic control unit (ECU). A throttle position control signal can be used, for example, for determining load demand by the operator and can relate acceleration and deceleration information to the ECU.
Some such engine control systems may also include a neutral position switch that is operable to indicate the position of the throttle lever in the xe2x80x9cneutralxe2x80x9d position. This type of switch is commonly used in engine control systems, such as in marine applications, wherein the throttle lever position controls both the transmission driven by the engine as well as the throttle.
In most applications using the above described control systems, the assembly of the control system can entail laborious calibration or synchronization to assure proper correlation between the position of a throttle lever and the throttle lever control signal. Such calibration is necessary to account for variation in performance or sensitivity of the position sensor, and the manner in which the sensor is mounted to monitor the throttle lever position.
Recalibration of such an engine control system may be necessary after a period of engine operation or after control system maintenance or repair. Such calibration is critical to control systems using an ECU, and is often performed by skilled personnel.
There is a need, therefore, for an improved method of calibration which overcomes these drawbacks of prior art devices. There is a particular need for a reliable method for automatically calibrating a throttle. Moreover, there is presently a need for a throttle arrangement which can utilize a method for automatically calibrating a position sensor.
The invention provides a novel system and method designed to respond to these needs. The invention features a method of calibrating a position sensor having a variable output corresponding to the position of a movable member. The method comprises establishing a first output of a position sensor corresponding to a first position of a moveable member. The first output in the featured method is a function of at least one first output stored in memory from a previous operating session. The method may also include establishing the first output as a function of a correction factor, as well a function of at least one first output stored in memory from a previous operating session. The function establishing the first output may include averaging a plurality of first outputs stored in memory from previous operating sessions and a correction factor. The method may include assigning a first output if there is no first output stored in memory. The method may also include establishing a second output of a position sensor corresponding to a second position of a moveable member. The second output may be a function of a correction factor and at least one second output stored in memory from a previous operating session.
According to another aspect of the invention, a method of calibrating a throttle position sensor for an internal combustion engine is featured. The throttle position sensor having a variable output corresponding to movement of the throttle. The method includes storing in memory a first output corresponding to a first position of the throttle from one engine operating session. The method also includes establishing the first output corresponding to the first position of the throttle for a subsequent engine operating session as a function of the first output stored in memory. The method may also include establishing the first output for a second engine operating session as a function of a correction factor. The method may also include establishing a maximum output corresponding to the first position, the maximum output being greater than or equal to the first output. The maximum output may be established as the first output for a second engine operating session, if the first output for a subsequent engine operating session is greater than the maximum output.
According to another aspect of the present invention, an internal combustion engine having a variable position throttle, an electronic memory, and a throttle position sensor is featured. The throttle position sensor produces a variable output corresponding to movement of the variable position throttle. The throttle position sensor is calibrated between a first position of the variable position throttle and a second position of the variable position throttle. In the first position a first output value is produced and in the second position a second output value is produced. Either or both the first output value or second output value from a first engine operating session is stored in memory. The first output value for a second engine operating session is established as a function of the first output value stored in memory from the first engine operating session or the second output value for the second engine operating session is established as a function of the second output value stored in memory from the first engine operating session. The first position of the throttle may correspond to a neutral or idle position and the second position may correspond to a full or wide-open throttle position. The internal combustion engine may produce an output representing the variable throttle position as a percentage of wide-open throttle position. The first output value or second output value for a second engine operating session may also be established as a function of a biasing value.